The chairman of Russia's Presidential Council for Civil Society and Human Rights says there is "not the slightest basis" for the piracy charges being leveled against Greenpeace activists arrested during an Arctic protest at a Russian state-owned oil rig last month.

Mikhail Fedotov expressed his opinion on October 3 as Russian investigators in the far northwestern city of Murmansk formally charged all 30 Greenpeace activists detained for their protest against Russia's offshore oil drilling.

The activists, including four Russians and 26 foreign nationals, were detained by Russian authorities in September after two of them tried to scale a Gazprom offshore drilling platform in Arctic waters.

Authorities seized Greenpeace's ship and towed it to Murmansk with the crew and activists aboard.

Greenpeace has described the charges as "extreme and disproportionate."

If found guilty, those indicted could face up to 15 years in prison.

First Offshore Arctic Rig

The platform, which the activists tried to scale, belongs to Gazprom's oil subsidiary. It is the first offshore rig in the Arctic. It was deployed to the vast Prirazlomnaya oil field in the Pechora Sea in 2011, but its launch was delayed by technological challenges.

Gazprom said in September it was going to start pumping oil this year but did not provide the exact date.

Greenpeace held a similar protest at the same oil platform last year without incurring any punishment.

Talking to activists of the ruling United Russia party on October 3, Putin said Moscow will expand its presence in the Arctic and restore a Soviet-era military base there to protect shipping routes across the Arctic Ocean.

Putin said the Arctic region is essential for Russia's economic and security interests.

Russia, the U.S., Canada, Denmark and Norway have all been trying to assert jurisdiction over parts of the Arctic, believed to hold up to a quarter of the Earth's undiscovered oil and gas.